1. Field of the Invention
The present invention relates to a breakable bolt assembly, and particularly, but not limited to, a breakable bolt assembly especially useful for securing a mud flap to a hanger.
Currently, the standard truck mud flap bolt is 3/8 inches in diameter and 1-2 inches long. It is a steel bolt. The top edge of the mud flap has mounting holes to receive the bolt. The mud flap is secured to a hanger which is attached to the truck by mounting the bolts through the mud flap and through the holes in the hanger. Standard hex head bolts and hand or power tools are needed to mount the mud flap to the hanger.
It is important that the bolt be strong enough to hold the mud flap, which is usually at least 1/2 inch thick. The hanger is typically made from steel or formed from welded iron bar stock. The average mud flap weights approximately 10-30 pounds, and in use, as much as 100 pounds of snow and ice can accumulate on the flap. This places substantial stress on the bolts.
In addition, the bolt assembly must also withstand the forces associated with twisting, turning, vibration, as well as the forces associated with downward stress. Moreover, there is significant stress placed on the mud flap when the truck travels at speeds of 55-60 miles per hour. The mounting orientation of the mud flap becomes altered from these forces, and is prone to more serious damage.
Specifically, a critical stress on the mud flap occurs when a truck backs up over a contorted mud flap. When this occurs, the mud flap is usually torn off the hanger, the mounting holes of the flap can be destroyed and, therefore, the mud flap is no longer usable by the driver until it is repaired or replaced, which can be time consuming and expensive. Oftentimes, the hanger also is destroyed.
Furthermore, an aluminum bolt cannot be used with a steel hanger because a galvanic reaction will occur between the two metals. Even if steel bolts are used with a steel hanger, the steel bolts rust from moisture and harsh environments, thus deteriorating the bolt. The bolts become damaged at the threads by impact with rocks, or often road tar adheres to the bolt. This making it difficult or nearly impossible to remove the bolt.
2. Prior Art
U.S. Pat. Nos. 3,258,887 to Mostoller; 2,826,428 to Lincoln; 3,778,086 to Moore et al.; 3,822,897 to Heath; 3,158,386 to Tillinghast; and 3,695,215 to Black are relevant to the present invention.
The Mostoller patent discloses a bolt designed to separate from the fasteners and materials it is attached to in the event of an explosion. Specifically, the Mostoller bolt comprises a standard bolt with a single reduced shank on a portion of the shaft and is designed to fail upon a sudden force tearing away the bolt.
The Lincoln patent discloses a replaceable splash guard featuring a wing nut which can be installed by hand, but usually requires a tool to remove. This device makes no provision for the avoidance of damage to the hanger if the mud flap is subjected to large magnitudes of shear force.
The Moore patent discloses a mud flap mounting means featuring a spring loaded clamp which is designed to open when a downward stress occurs, releasing the mud flap unharmed. A problem with this device is that it is readily exposed to the elements and is susceptible to damage from road tar, stones, dust and grit. The solution provided by the Moore patent, like so many others in the industry, requires special mud flap hangers, clamps, hinges, springs, etc. Consequently, this is a very costly solution by comparison to the standard bolt assemblies.
The Heath patent discloses a perforated mud flap that will separate after a certain stress is reached when the truck backs over the mud flap. The perforations reduce the strength of the mud flap to about 1/5 of the standard mud flap, which is 100 ft/lbs of shear. Unfortunately, the concept is not practical because 100 ft/lbs of shear is reached almost immediately when a tire backs over a mud flap.
The Tillinghast patent discloses a specially designed slotted mud flap bushing and clamp device that will allow for the flap to release from the hanger before harm occurs to the flap. If this occurs satisfactorily, the user must remove the bolt mountings to re-install the mud flap. The designs of the mountings and materials used are subject to corrosion and road damage, which would make re-mounting a problem. Consequently, the device has not been accepted well in the industry.
The Black patent discloses a perforated weakened mud flap which is designed to tear off in sections if backed over. This makes possible the use of the same flap more than once if it is backed over, but the remaining flap is smaller than before.
The shortcomings in the prior art endeavors are clear. There is a need to provide an inexpensive bolt assembly to mount and repair the mounting of standard mud flaps without requiring special hangers, tools, clamps and the like.